1. Field of the Invention
This invention relates generally to a method of controlling the inflammatory response. The invention has broad applicability in inflammatory diseases or processes to control or alter inflammation.
2. Background Art
Inflammation is a complex stereotypical reaction of the body expressing the response to damage of cells and vascularized tissues. The discovery of the detailed processes of inflammation has revealed a close relationship between inflammation and the immune response. The main features of the inflammatory response are vasodilation, i.e. widening of the blood vessels to increase the blood flow to the infected area; increased vascular permeability, which allows diffusible components to enter the site; cellular infiltration by chemotaxis, or the directed movement of inflammatory cells through the walls of blood vessels into the site of injury; changes in biosynthetic, metabolic, and catabolic profiles of many organs; and activation of cells of the immune system as well as of complex enzymatic systems of blood plasma.
There are two forms of inflammation, acute and chronic. Acute inflammation can be divided into several phases. The earliest, gross event of an inflammatory response is temporary vasoconstriction, i.e. narrowing of blood vessels caused by contraction of smooth muscle in the vessel walls, which can be seen as blanching (whitening) of the skin. This is followed by several phases that occur over minutes, hours and days later. The first is the acute vascular response, which follows within seconds of the tissue injury and lasts for several minutes. This results from vasodilation and increased capillary permeability due to alterations in the vascular endothelium, which leads to increased blood flow (hyperemia) that causes redness (erythema) and the entry of fluid into the tissues (edema).
The acute vascular response can be followed by an acute cellular response, which takes place over the next few hours. The hallmark of this phase is the appearance of granulocytes, particularly neutrophils, in the tissues. These cells first attach themselves to the endothelial cells within the blood vessels (margination) and then cross into the surrounding tissue (diapedesis). During this phase erythrocytes may also leak into the tissues and a hemorrhage can occur. If the vessel is damaged, fibrinogen and fibronectin are deposited at the site of injury, platelets aggregate and become activated, and the red cells stack together in what are called “rouleau” to help stop bleeding and aid clot formation. The dead and dying cells contribute to pus formation. If the damage is sufficiently severe, a chronic cellular response may follow over the next few days. A characteristic of this phase of inflammation is the appearance of a mononuclear cell infiltrate composed of macrophages and lymphocytes. The macrophages are involved in microbial killing, in clearing up cellular and tissue debris, and in remodeling of tissues.
Chronic inflammation is an inflammatory response of prolonged duration—weeks, months, or even indefinitely—whose extended time course is provoked by persistence of the causative stimulus to inflammation in the tissue. The inflammatory process inevitably causes tissue damage and is accompanied by simultaneous attempts at healing and repair. The exact nature, extent and time course of chronic inflammation is variable, and depends on a balance between the causative agent and the attempts of the body to remove it. Etiological agents producing chronic inflammation include: (i) infectious organisms that can avoid or resist host defenses and so persist in the tissue for a prolonged period. Examples include Mycobacterium tuberculosis, Actinomycetes, and numerous fungi, protozoa and metazoal parasites. Such organisms are in general able to avoid phagocytosis or survive within phagocytic cells, and tend not to produce toxins causing acute tissue damage. (ii) Infectious organisms that are not innately resistant but persist in damaged regions where they are protected from host defenses. An example is bacteria which grow in the pus within an undrained abscess cavity, where they are protected both from host immunity and from blood-borne therapeutic agents, e.g. antibiotics. Some locations are particularly prone to chronic abscess formation, e.g. bone, and pleural cavities. (iii) Irritant non-living foreign material that cannot be removed by enzymatic breakdown or phagocytosis. Examples include a wide range of materials implanted into wounds (wood splinters, grit, metals and plastics), inhaled (silica dust and other particles or fibers), or deliberately introduced (surgical prostheses, sutures, etc.) Also included are transplants. Dead tissue components that cannot be broken down may have similar effects, e.g. keratin squames from a ruptured epidermoid cyst or fragments of dead bone (sequestrum) in osteomyelitis. (iv) In some cases the stimulus to chronic inflammation may be a normal tissue component. This occurs in inflammatory diseases where the disease process is initiated and maintained because of an abnormality in the regulation of the body's immune response to its own tissues—the so-called auto-immune diseases. (v) For many diseases characterized by a chronic inflammatory pathological process the underlying cause remains unknown. An example is Crohn's disease.
Examples of chronic inflammatory diseases include tuberculosis, chronic cholecystitis, bronchiectasis, rheumatoid arthritis, Hashimoto's thyroiditis, inflammatory bowel disease (ulcerative colitis and Crohn's disease), silicosis and other pneumoconiosis, and implanted foreign body in a wound.
Activation of innate immunity and promotion of inflammation are common responses to replication incompetent adenoviruses (Ad) now being developed as vectors for gene therapy (Jooss, K. (2003) Gene Ther. 10:955-963; Zaiss, A. K. (2002) J. Virol. 76:4580-4590). The complement system is central to both innate immunity and inflammation (Walport, M. J. (2001) N Eng J Med 344:1058-1066 and 1140-1144). Because it is comprised of multiple membrane-bound and blood factors, the complement system is of particular relevance in delivery of vectors administered intravenously. In fact, Cichon et al. showed complement was activated in a majority of human plasma samples when challenged with different adenoviral serotypes; complement activation was completely dependent on anti-Ad antibody (Cichon (2001) Gene Ther 8:1794-1800).
The complement mediated inactivation is a multistep enzymatic cascade which finally results in formation of a membrane attack complex (MAC) mediating the perforation of membranes and subsequent lysis of the invading organism. It is either initiated by antigen-antibody complexes (classical pathway) or via an antibody independent pathway which is activated by certain particular polysaccharides, viruses and bacteria (alternative pathway).
Human organs and cells themselves are protected to complement mediated lysis. This protection is achieved by expression of complement inactivation factors. So far, five human factors are known. CD35 (CR1) is released from the cells and acts mainly extrinsically. In contrast, CD59, CD46 (MCP), CD55 (DAF) and HRF are integrated into the cellular membrane. CD46 (MCP) is a classical transmembrane protein while HRF, CD59 and CD55 are GPI-anchored. These factors can interrupt the complement cascade at two different stages: DAF, CR1 and MCP act at an early stage of both the alternative and the classical pathway. In contrast, CD59 and HRF inhibit the assembly of the membrane attack complex, which is the final step of both pathways resulting in channel formation and lysis.
The early pro-inflammatory cascade can be initiated by endotoxin (also known as lipopolysaccharide, or LPS). LPS is one of the major constituents of the cell walls of gram-negative bacteria. Recognition of conserved microbial products, such as LPS, by the innate immune system leads to a variety of signal transduction pathways. These signal transduction pathways mediate the induction and secretion of cytokines that can regulate the level and duration of an inflammatory response. The systemic inflammatory response that accompanies endotoxic shock (caused by triggers such as the presence of LPS) is controlled by the levels of pro- and anti-inflammatory cytokines. Although the production of pro-inflammatory cytokines by cells of the innate immune system play an important role in mediating the initial host defense against invading pathogens (O'Neill, 2000), an inability to regulate the nature or duration of the host's inflammatory response can often mediate detrimental host effects as observed in chronic inflammatory diseases. Additionally, in the early stages of sepsis, the host's inflammatory response is believed to be in a hyperactive state with a predominant increase in the production of pro-inflammatory cytokines that mediate host tissue injury and lethal shock (Cohen, 2002). In this regard, the ability to suppress pro-inflammatory cytokines and/or enhance anti-inflammatory cytokines, i.e. IL-10, has been shown to severely reduce the toxic effects of endotoxin (Berg, 1995; Howard, 1993).
Past studies have identified that the phosphatidylinositol 3-kinase (PI3K) pathway can limit the production of TNF-α and IL-12 upon TLR-stimulation (Fukao, 2002; Fukao, 2002; Guha, 2002). Moreover, it has been demonstrated that the utilization of the PI3K pathway by a TLR2-agonist resulted in enhanced IL-10 production whereas the levels of IL-12 were reduced (Martin, 2003).
However, there remains a distinct need in the art for methods and compositions capable of regulating cytokine production, thereby controlling inflammation and associated disorders.